1. Field of the Invention
The present invention generally relates to a digital image processing apparatus, and more specifically to a technique preferably adapted to software for a printer, a facsimile machine, a digital camera, a personal computer, and the like.
2. Description of the Related Art
Recently, the image resolution of image input devices such as a flat bed scanner and a digital camera has been remarkably improved. However, the image resolution of display devices displaying the images input by such input devices is not so high as that of the input devices. For example, there are so many digital cameras having resolutions of 4 through 5 million pixels, but the resolutions of liquid crystal displays for personal computers are still 1.3 million pixels for SXGA and 2 million pixels for UXGA. Further, the resolution of a liquid crystal display attached to a digital camera is even lower. As a result, the resolution of an image input by an image input device needs to be reduced when viewed on a display.
Unfortunately, when the image is viewed with reduced resolution, necessary information may not be obtained in many cases. For example, a case where a picture of a person is taken with a digital camera is considered. When pictures are taken, plural same pictures may be taken to get a best shot. However, in typical use of such a digital camera, since the data storage capacity of the camera is limited, the user is more likely to delete some unnecessary plural pictures when the capacity is running out. In this case, the user may view the attached liquid crystal display to select pictures to be deleted. Unfortunately, there may be many cases where the eyes of the person are closed when the pictures are viewed on a display of a personal computer. To avoid such problems, there may be a method of enlarging a part of a picture that has been shrunk. However, there is a problem that it is very troublesome to perform the same operations of enlarging and moving with respect to plural pictures.
To solve the problem, Patent Document 1 discloses a technique in which selected plural images are displayed on the same display; when enlarge, shrink, and move operations are performed on one of the plural pictures, the same operations are also applied to the other pictures displayed on the display. By doing this, it is possible to determine whether the eyes of the person are closed with fewer operations. In addition, it is not to hard to anticipate that this technique of Patent Document 1 is useful when applied to a document image scanned by a flat bed scanner. For example, when this technique is applied to document images viewed as the same document when viewed in a list in a thumbnail grid mode, it is possible to effectively view a selected part of each document where important information is included.
Patent Document 1: Japanese Patent Application Publication No. 2006-5640
Non Patent Document 1: 1C. Cortes and V. N. Vapnik “Support Vector Networks,” Machine Learning, vol. 20, pp. 273-297, 1995
Non Patent Document 2: N. Otsu, and T. Kurita, “A new scheme for practical, flexible and intelligent vision system,” Proc. IAPR Workshop on Computer Vision, pp. 431-435, 1988.
However, it is not necessarily the case that all the document images scanned by a flat bed scanner have exactly the same layout.
As an example, FIGS. 1A through 1D illustrate such a case where a snapshot (picture) of a person is taken. FIG. 1A is a first picture of the person. As shown in FIG. 1A, the person is displayed in the center of the picture. FIG. 1B is an enlarged image of the area surrounded by the rectangle in FIG. 1A. After a few seconds, a next picture is taken to get a best shot. FIG. 1C is a second picture of the person. As shown in FIG. 1C, the person is moved to the left-hand side of the picture. Now, FIG. 1D is another enlarged image of the area surrounded by the rectangle in FIG. 1C. The positions of the rectangles in FIGS. 1A and 1C are the same with respect to the corresponding pictures. As a result, as shown in FIG. 1D, the face of the person is not included in FIG. 1D. In such a case like this, it is necessary to slightly adjust the enlarged (noticed) area so as to see the face of the person as shown in FIG. 1B. As described, there may be cases where necessary information is not included in the same noticed areas when the position is slightly moved among plural pictures.
The above case may be relatively extreme because the person is moved a large distance from the center position, and the above case may not be likely to occur in a typical photo shoot. However, when an enlargement factor is large, that is, when the noticed area is relatively small compared with the original image including the noticed area, the same problem as described above may occur. For example, a display device attached to a typical digital camera is very small. Therefore, to check an image on the display device carefully, the image is required to be sufficiently enlarged. As another example, there may be a case where the face of a person is very small when, for example, a group of people are included in a picture. In such a case, it is also required to sufficiently enlarge the necessary area of the picture. When these cases are considered, a camera shaking in a photo shoot may become a serious mistake in the photo shoot.